Techniques for a production of a polyketone from ethylene, propylene or the like .alpha.-olefin and carbon monoxide are well known.
For example, M. M. Brubaker et al. have reported a process for the production of a polyketone from ethylene and carbon monoxide in the presence of a radical initiator (J. Amer. Chem. Soc., 74, 1509 (1952)). Also, U.S. Pat. No. 2,577,208 (1951) discloses a process for the production of a polyketone from ethylene and carbon monoxide in the presence of a nickel catalyst.
However, since these polyketone production processes require reaction under a high pressure and the reaction of ethylene with carbon monoxide has no regularity, the resulting polyketone has low crystallinity and poor mechanical strength.
The term "regularity of reaction" as used herein firstly relates to the reaction order of a mono-substituted ethylene and carbon monoxide. The first case is as follows: when a mono-substituted ethylene and carbon monoxide do not react with each other in alternating fashion, a poly-substituted-ethylene moiety in which the mono-substituted ethylene molecules alone are polymerized is formed and carbon atoms having substituent groups in this moiety lose asymmetry, so that the resulting polyketone shows reduced optical activity.
The second case is regularity of the binding mode of a mono-substituted ethylene to carbonyl group (positional regularity). This is divided into a head to a head type, a head to tail type and a tail to tail type. The reaction is regular when the head to tail type binding is perfectly made.
The third case is a regularity formed by the binding mode of polymer-specific substituent groups (stereoregularity). Isotactic and syndiotactic are regular, but a completely random case is called atactic which is irregular.
The fourth case is chirality of newly formed asymmetric carbon. When a mono-substituted ethylene and carbon monoxide copolymerize in alternating fashion, carbon atoms to which substituent groups are linked become asymmetric carbons and a polymer is constituted from only one antipode, the resulting polyketone is isotactic and such a polyketone becomes an optically active polymer. When chirality is formed alternately, the polymer becomes syndiotactic having a relatively small angle of rotation.
A. Sen et al. have reported a polymerization reaction of an olefin and carbon monoxide in which [Pd(CH.sub.3 CN).sub.4 ](BF.sub.4).sub.2 (PPh.sub.3).sub.n (n=1 to 3) is used as a catalyst (J. Amer. Chem. Soc., 104, 3520 (1982)). According to this method, olefin and carbon monoxide are polymerized by alternating reaction, thus achieving the first case of the aforementioned regularities of reaction, but still leaving other regularities unsettled.
NL 84 03,035 (1984), EP 121,965 (1984) and EP 181,014 (1984) disclose polyketone production processes which use a complex of Pd(II), Co(II) or Ni(II) with a divalent ligand represented by RR.sub.1 M(CR.sub.4 R.sub.5)MR.sub.2 R.sub.3 (wherein M represents an element from P, As or Sb, each of R, R.sub.1, R.sub.2 and R.sub.3 represents a hydrocarbon radical and each of R.sub.4 and R.sub.5 represents hydrogen or a hydrocarbon radical which has no steric hindrance).
Also, a copolymerization reaction in which a complex with a nitrogen-containing bidentate ligand such as bipyridine is used as a catalyst has been disclosed in JP-A-62-131025 (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
Making use of such bidentate ligand complexes, processes for the production of a polyketone from a substituted ethylene such as propylene, styrene or the like and carbon monoxide have been disclosed (EP 229,408 (1986), JP-A-62-131025). For example, M. Barsacchi et al. (Angew. Chem. Int. Ed. Engl., 30, 989 (1991)) have carried out copolymerization of styrene and carbon monoxide using (1,10-phenanthroline)Pd(p-CH.sub.3 C.sub.6 H.sub.4 SO.sub.3).sub.2 as a catalyst and reported that the reaction was alternating and a syndiotactic binding mode was frequent as a stereochemistry of the substituent group. Polymerization of carbon monoxide with propylene or the like using a bidentate ligand complex has been disclosed in EP 376,364 (1989), EP 384,517 (1989), JP-A-2-189337 and JP-A-2-247223, but the aforementioned syndiotactic stereoselectivity is still low.
In addition, with regard to the synthesis of an optically active polyketone, the following report, for example, has recently been published.
A. Sen et al. have reported on the synthesis of an optically active polyketone by copolymerization of ethylene, propylene or styrene with carbon monoxide using a complex of an optically active bidentate ligand and divalent palladium as a catalyst (Polym. Prepr., 35, 676,1994; Macromolecules, 27, 2694, 1994). According to these reports, in the case of the copolymerization of propylene with CO carried out using a ligand ((R)-(+)-BINAP) represented by the following formula ##STR2## as an optically active ligand, the thus obtained polyketone showed a molecular weight of 3,100 and the turn over number (a value obtained by converting the yield of polymer per mole of catalyst into monomer mole numbers, to be referred to as "TO number" hereinafter) of 440. Positional selectivity of the reaction was 66% in the head to tail type, thus showing low positional regularity of the reaction (second regularity), and the [.PHI.].sub.D.sup.20 value was +25.degree. (CH.sub.2 Cl.sub.2). The term [.PHI.] is represented by the formula [.PHI.]=[.alpha.].times.M/100 wherein [.alpha.] is specific rotation and M is molecular weight of the high molecular weight repeating unit. In the case of the copolymerization of styrene with carbon monoxide (to be referred to as "CO" hereinafter in some cases), the resulting polyketone has only 4% of isotactic bonding, thus showing extremely low stereoregularity.
G. Consiglio et al. have carried out copolymerization of propylene with CO using a complex composed of a bidentate ligand 2,4-pentadienylbis(diphenylphosphine) (to be referred to as "BDPP" hereinafter) represented by the following formula ##STR3## and divalent palladium and reported that about 83% of the product was head to tail type (Angew. Chem. Int. Ed. Engl., 31, 303, 1992). Though positional regularity (second regularity) of the reaction was improved, positional selectivity of the reaction was still low.
S. Bronco et al. have obtained a polyketone by carrying out copolymerization of propylene with CO using Pd(II) or Ni(II) as a catalyst in the presence of a diphosphine ligand (S)-6,6'-dimethylbiphenyl-2,2'-diyl)bis(dicyclohexylphoshine) (to be referred to as "(S)-BICHEP" hereinafter) represented by the following formula ##STR4## and 1,4-naphthoquinone (Macromolecules, 27, 4436, 1994). That is, a polyketone having a number-average molecular weight (Mn) of 3,400 was obtained by carrying out 192 hours of reaction under a CO pressure of 42 atmospheres at 42.degree. C. The TO number was 1,640, but the yield from propylene was 17.7% Th, which was low. The [.PHI.].sub.D.sup.20 value was +18.degree. (c, 0.97, (CF.sub.3).sub.2 CHOH), which was small, showing insufficient stereoregularity of the reaction.
Also, M. Brookhart et al. have reported on the relation of bidentate ligand to stereoregularity in the copolymerization of 4-tert-butylstyrene with CO produced using a Pd catalyst having the following bidentate ligand ##STR5## wherein Ar represents, 3,5-bistrifluoromethylphenyl group (J. Amer. Chem. Soc., 116, 3641, 1994). They report that 90% at the maximum is syndiotactic when the bidentate ligand is 2,2-bipyridine or 2,2-bipyrimidine, and an isotactic polyketone is obtained when an optically active bisoxazoline is used. Also, according to this report, a polyketone having a molecular weight (Mn) of 26,000 is obtained with a yield of 21.5% Th from p-tert-butylstyrene by carrying out 72 hours of copolymerization reaction of p-tert-butylstyrene at 25.degree. C. under a CO pressure of 1 atmosphere using a catalyst of the following bidentate ligand in which R is i-Pr ##STR6## wherein Ar represents 3,5-bistrifluoromethylphenyl group). The TO number was 100 showing low catalytic activity. The [.PHI.].sub.D.sup.20 value was -536.degree..